Vasoocclusion devices are surgical implements that are placed within the vasculature of the human body, typically via a catheter, to block the flow of blood through the vessel making up that portion of the vasculature or within an aneurysm stemming from the vessel. One widely used vasoocclusive device is a helical wire coil having windings that are dimensioned to engage the walls of the vessels. Fibers may also be woven or laid crosswise through the windings to provide a substrate for clot formation and tissues growth within the chosen site. Coils having such a structure are readily commercially available.
U.S. Pat. No. 4,994,069, to Richart et al., describes a vasoocclusive coil which assumes a linear helical configuration when stretched, and a folded convoluted configuration when relaxed. The coil is introduced into the human body in a stretched condition. When the coil reaches its intended site, the coil assumes its relaxed condition--which is better suited to occlude the vessel--and restricts blood flow beyond the space that it occupies.
U.S. patent application Ser. No. 07/771,013, to Chee et al., teaches a helical vasoocclusion coil to which fibrous elements are attached in such a way that they will not be dislodged from the coil. The fibrous elements enhance the ability of the coil to fill space within the vasculature and to facilitate clot formation and tissue growth.
Care must be taken in creating combination fibrous coils, i.e., those containing metal coils and fibrous elements, since the fibrous elements may come off and move to vessels supplying blood to normal tissue. Fibrous elements, since they are not normally radiopaque, are difficult to find and to retrieve if separated from the metallic coil. Nevertheless, it is desireable to increase the ratio of fibrous element to the metallic coil since the fibrous element increases the tendency at the coil assembly to cause embolic and tissue growth.
The inventive coil assembly is desireable in that the ratio of fibrous material to metallic material is quite high, the fibrous material is held firmly in place due to the braided or woven configuration, and is easily placed within the body's vasculature.